Stage 1 Biology B Exam

Question 1

Name the two main physical barriers that prevent the invasion of pathogens in the first line of the body’s defence.

Answer 1

Skin and mucus.

Question 2

What are the chemical barriers included in the first line of defence?

Answer 2

Acid from sweat on the skin, enzymes within saliva, mucus and tears - as well as stomach acid.

Question 3

What is mucus?

Answer 3

A thin, clear liquid which consists of water, salts, and immune cells.

Question 4

What is the function of mucus and how does it defend the body?

Answer 4

The viscous and sticky substance traps pathogenic cells and prevents them from entering the body. Immune cells also help to attack pathogens.

Question 5

Where is mucus-secreting tissue located?

Answer 5

Nose, mouth, throat and lungs.

Question 6

What is the complement system and how does it work?

Answer 6

The complement system consists of at least 20 complement proteins that circulate through the blood. They work by binding to bacterial cell membranes and creating pores in its cell wall. This allows water and salts to flood the bacterium and cause it to swell and burst. This is known as lysis. These proteins can also assist other immune functions such as phagocytosis and pathogen flagging.

Question 7

What is another term used for ‘white blood cells?’

Answer 7

Leukocytes.

Question 8

What are the four types of leukocytes?

Answer 8

Macrophage, Natural Killer (NK) cell, Eosinophil, and Neutrophil.

Question 9

Which of the four leukocytes are phagocytic cells?

Answer 9

Macrophages and neutrophil.

Question 10

What do phagocytes do?

Answer 10

Phagocytes remove pathogenic cells through a process known as phagocytosis, where the pathogen is engulfed and digested by the cell.

Question 11

Describe the process of phagocytosis.

Answer 11

Pseudopodia (legs) of a pathogen surround and trap it. The pathogen(s) is then engulfed through endocytosis, where a VACUOLE is formed around it. The vacuole and a lysosome containing enzymes fuse together. This exposes the contained pathogen to the enzymes and other toxic compounds, killing it. Debris from the destroyed pathogen exit the phagocyte through exocytosis.

Question 12

What is the organelle involved in phagocytosis?

Answer 12

Macrophages internalise pathogens through phagocytosis, entrapping them into organelles called phagosomes. Phagosomes then fuse with lysosomes to mature into phagolysosomes, acquiring an acidic and hydrolytic lumen that kills the pathogens.

Answer: Phagosomes or phagolysosomes

Question 13

What is the role of Natural Killer Cells?

Answer 13

Circulating through the blood, the function of NK cells is to locate abnormal cells, which can be infected, cancerous, etc. They then either release cytokine chemicals to cause cell death by lysis, or apoptosis (programmed cell death).

Question 14

What is the role of Eosinophils?

Answer 14

Eosinophils protect your body by assisting inflammation and fighting pathogens that phagocytic cells cannot.

Question 15

What is the role of histamine and how does it help the body fight off pathogens?

Answer 15

In the presence of an injured and/or infected area, white blood cells will release histamine and cytokine proteins to said area. This stimulates the surrounding blood vessels and instigates dilation. This allows more fluid release to the area causing swelling. This allows more immune cells to flood the area and fight off pathogens. This is known as inflammation, which causes redness, pain, swelling, heat, and loss of function in the affected area.

Question 16

What does pus consist of?

Answer 16

Pus, a thick opaque yellowish white substance, is formed usually as a product of inflammation due to invasion of the body by pathogens. It consists of dead/degenerating white blood cells/leukocytes, tissue debris, and living or dead microorganisms.

Question 17

What is fever a result of?

Answer 17

A fever is a part of the nonspecific immune response, where the body instigates a temporary rise (constriction and contraction of vessels and muscles, trapping heat) in body temperature. This occurs when the body is attempting to kill off pathogens with heat.

Question 18

Define an infectious and non-infectious disease.

Answer 18

An infectious disease is a deviation in cell biology and structure in an organism that is not a direct result of physical injury, caused by microorganisms. A non-infectious disease is the same thing, but is congenital and/or caused by genetics.

Question 19

Define:
- Infection
- Host
- Pathogen

Answer 19

• The successful entry of a pathogen into the body. This does not necessarily mean disease will ensue, as the innate and adaptive immune system can still fight it off.
• The organism which allows the pathogen to cause infection within it.
• A microbe which is dangerous and can cause disease.

Question 20

What is the role of the human microbiome?

Answer 20

The human microbiome, a personal bunch of helpful bacteria on and in the human body, helps kill external and potentially dangerous bacteria.

Question 21

What are the 5 main causes of infectious disease?

Answer 21

• Bacteria (prokaryotic cells)
• Viruses (non-living)
• Protozoans (single-celled eukaryotes)
• Fungi (yeasts and moulds)
• Parasites (multicellular eukaryotic animals)

Question 22

Describe how pathogens adhere and enter the cell.

Answer 22

• Exposure to pathogen
• Adherence of pathogen to skin (OCCURS through binding of complementary proteins on the surface of the pathogen to the receptors on the host cell membrane), microbiome can kill it off at this point
• Invasion through openings in the body’s defence (openings in skin like cuts, through the mouth, nose, eyes, etc.)
• Infection in the cells and tissue fluid
• This can lead to toxicity and/or invasion of other tissue
• Which leads to tissue damage, causing disease

Question 23

Describe the process through which bacteria and viruses cause disease.

Answer 23

Once bacteria and viruses successfully adhere and penetrate the host’s cell membrane, they go about similar processes to initiate disease. Bacteria tend to invade the membrane and replicate through asexual binary fission, which then causes tissue damage and disease. Viruses enter cells and hijack their biochemistry by releasing their RNA/DNA within, making host cells replicate the virus.

Question 24

What are the factors that affect disease?

Answer 24

Disease can be influenced by:

• Type of pathogen, (Covid, influenza)
• Microbiome of host
• Age of host
• Season
• Lifestyle (stress, diet, air pollution, sleep, proximity to potential pathogens)
• Genome of host
• State of immune system

Question 25

What is endocytosis?

Answer 25

Endocytosis is a general term describing a process by which cells absorb external material by engulfing it with the cell membrane and forming a vesicle around it within.

Question 26

What is virulence and what affects it?

Answer 26

Virulence is the measure of the ability of a pathogen to cause disease.

It depends on:

• Numerous virulence factors of the pathogen
• The host (pathogens are highly specific for certain organisms)
• Environmental conditions (weather, season, location, etc. Viruses are much more infectious during winter due to less external damage of its RNA/DNA from heat and UV.)

Question 27

Through what ways are diseases transmitted?

Answer 27

Pathogens can be transmitted between hosts through:

• Air (airborne)
• Dust
• Direct contact
• Faeces
• Food
• Animals

Question 28

What is a vector?

Answer 28

A vector is an animal which spreads pathogens from one host to another without suffering any harm itself.

Question 29

Define:
- Disinfectant
- Antiseptic
- Antibiotic
- Antiviral
- Antifungal

Answer 29

A disinfectant is a decontaminant, a liquid chemical which destroys microorganisms on non-living surfaces.

An antiseptic is a liquid chemical that is applied to the skin and/or wounds to reduce the number of microorganisms living there.

An antibiotic is an antibacterial agent which is used to treat bacterial infections and diseases.

An antiviral is a medication which targets specific viruses and prevents them from attaching to and infecting healthy cells, as well as preventing it from multiplying.

An antifungal is a medication which is used to treat fungal infections by directly applying the substance, typically as a cream from a tube, to the infected region.

Question 30

When could a possibly harmless microbe become pathogenic?

Answer 30

If someone’s microbiome and/or immune system is weak, then microbes that wouldn’t usually harm others with adequate microbiomes could harm them

Question 31

What are the factors that affect the survival of a pathogen?

Answer 31

The survival of a pathogen depends on:
1. Ability to enter cells
2. Availability of nutrients and removal of wastes
3. Environmental conditions (Temp, pH & moisture)
4. Ability to replicate and transmit to new hosts

Question 32

If a question is 5 marks in an exam, how many points should you make?

Answer 32

5 or more.

Question 33

Which class of organisms have an adaptive immune response?

Answer 33

Vertebrates only.

Question 34

What are antibodies and what do they do?

Answer 34

Antibodies, created by previous exposure to foreign molecules, recognise antigens, through foreign particles, e.g. a pathogen’s surface proteins. These antibodies neutralise and flag, or mark a pathogen for destruction by phagocytic cells of the innate immune system.

You can acquire antibodies through exposure and birth (i.e. breastfeeding).

Antibodies do not ‘actively search’ for antigens (e.g. surface proteins), they circulate the blood after being secreted by B-cells and have a chance to attach to a pathogen.

Antibodies can sometimes cause clumps of pathogens to stick together (agglutinate) which can increase the efficiency of phagocytosis.

Question 35

What are the types of T-cells?

Answer 35

A T-Helper cell can recognise antigens with its receptor. If it does, it attaches and releases a chemical which stimulates and signals plasma B-cells, which produce antibodies, and cytotoxic T-cells, which possess cytokine receptors to kill the infected cell through released enzymes.

Memory T-cells, much like memory B-cells, will retain a ‘memory’ of a specific pathogen and initiate a faster response when the body is exposed to it again. It does this by dividing into cytotoxic T-cells that instantly know specifically what to target.

Question 36

What are the types of B-cells?

Answer 36

Plasma B-cells secrete specific shaped antibodies which circulate through the blood and potentially bind to the specific complementary surface proteins (antigen) of their respective virus.

Antibodies can attach to B-cells to become Memory B-cells. These attached antibodies allow the B-cell to retain the ‘memory’ of that specific pathogen. If this pathogen infects the body again, memory B-cells can reactivate plasma B-cells to release specific antibodies.

Question 37

What is deoxyribonucleic acid? (DNA)

Answer 37

DNA stores the information that directs all the complex processes an organism must carry out.

It does this by containing genes that code for all of the organism’s proteins

Question 38

What does DNA consist of?

Answer 38

DNA is made up of 2 strands of polynucleotides that form a double helix.

Each strand of DNA has a sugar-phosphate backbone, and bases that bind to complementary bases on the other strand by weak hydrogen bonds.

Question 39

What are the bases of nucleotides and which complement each other?

Answer 39

The bases from one strand bind (by weak hydrogen bonds) to their complementary bases on the complementary strand.

ATCG

Adenine <–> Thymine
Cytosine <–> Guanine

Question 40

DNA vs. RNA?

Answer 40

DNA:
- Stores genetic information
- Double stranded
- Bases: Thymine, adenine, guanine, cytosine

RNA:
- Involved in protein synthesis
- Single stranded
- Bases: Uracil, adenine, guanine, cytosine

Question 41

What is the hierarchy of synthesis from DNA to amino acid?

Answer 41

DNA - made up of nucleotides provides the code for the cellular activities

RNA - also made up of nucleotides converts DNA code into RNA molecules to synthesise proteins to carry out cellular functions

Protein - made by the code on RNA molecules and carry out the cellular functions

Question 42

What is the process of protein synthesis and gene expression?

Answer 42

Step 1: Transcription (DNA to mRNA)

Genetic information in a gene is copied (transcribed) to messenger RNA (mRNA).

The part of the DNA to be transcribed unwinds, the two strands separate, and free floating RNA nucleotides assemble at the template DNA strand to form an mRNA molecule.

The main enzyme involved is called RNA polymerase.

mRNA carries the genetic message from the DNA to ribosomes in the cytoplasm for protein synthesis (translation).

Step 2: Translation (mRNA to protein)

Messenger RNA (mRNA) is transported from the nucleus to ribosomes in the cytoplasm.

The genetic message on the mRNA is translated into a sequence of amino acids (forming a polypeptide)

Polypeptides then fold into proteins

The genetic message in RNA is in the form of codons (three bases) that each code for a specific amino acid

Each amino acid is carried by a specific tRNA (transfer RNA) to a ribosome to add to the growing polypeptide chain.

Each tRNA has a specific set of three bases (anticodon) that complements each codon on the mRNA template

In the ribosome, tRNA molecules, carrying specific amino acids, bind (via their anticodons) to complementary codons in the mRNA. This adds amino acids to the growing polypeptide chain in the correct sequence.

Many antibiotics (chemicals that are anti-bacterial) work by inhibiting protein synthesis at the ribosome.

Question 43

What are macromolecules?

Answer 43

All organisms use four different types of large molecules:

Carbohydrates, Lipids, Protein and Nucleic acids (DNA and RNA)

Question 44

What are organic compounds?

Answer 44

Organic compounds contain carbon (C) and hydrogen (H) (can also contain O, N, S, and P)

They can be very complex (big)

Question 45

What are polymers?

Answer 45

Polymers are composed of many smaller molecules called subunits (monomers), that join together to make long chains.

Question 46

What are nucleic acids?

Answer 46

Nucleic acids (DNA & RNA) store, and help express the information that directs all the metabolic processes in organisms.

There are 2 types of nucleic acids:
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

Nucleic acids are polynucleotides that are made of subunits called nucleotides

Question 47

What is DNA made up of?

Answer 47

DNA is made up of 2 polynucleotide strands that form a double helix.

Each strand has a sugar-phosphate backbone, and bases that bind to complementary bases on the other strand by weak hydrogen bonds.

Question 48

What are genes and what do they do?

Answer 48

Genes are segments of DNA that provide the code to make the sequence of amino acids (polypeptides) for all the proteins in an organism.

Genes can also make RNA (that don’t code for proteins)

Question 49

What does RNA do?

Answer 49

Ribonucleic acid (RNA) helps convert the codes in DNA to the sequence of amino acids for all the proteins in an organism.

The flow of genetic information in a cell:
DNA (genes) → RNA → protein

RNA molecules also form structures (including ribosomes)

Question 50

What are the functions of proteins in the body?

Answer 50

Structural (eg, cytoskeleton, hair, nails, tendons, ligaments and skin)

Catalyse reactions (enzymes)

Movement (muscle fibres)

Transport (haemoglobin carrying O2, membrane transport proteins)

Defence (antibodies produced by white blood cells)

Communication (hormones and membrane receptors)

Question 51

What are proteins?

Answer 51

Proteins are made up of one or more polypeptide chains that are long chains of amino acid subgroups.

There are 21 different amino acids, each with different chemical properties, making up all the different proteins in your body.

Question 52

How is protein structure classified?

Answer 52

1. Primary structure
   - the sequence (order) of amino acids in a polypeptide chain
2. Secondary structure
   - the coiling or folding of parts of the polypeptide chain into helices and sheets.
   - Held in place by hydrogen bonds
3. Tertiary structure
   - the 3D shape of the entire folded polypeptide
   - helices and sheets (held together by hydrogen bonds) folded into one globular mass
4. Quaternary structure
   - the association of two or more polypeptide chains (only some proteins have a quaternary structure)

Question 53

What are carbohydrates?

Answer 53

Carbohydrates (saccharides) are molecules that contain carbon (C), hydrogen (H) and oxygen (O).

Made of simple sugars, such as glucose that are converted into usable energy (ATP) in cells

Monosaccharides
Simple form of an organic sugar.
Eg. Glucose, Fructose, Galactose

Disaccharides
Consist of 2 monosaccharides bound together.
Eg. Sucrose (1 glucose + 1 Fructose)

Polysaccharides
Long chains of monosaccharides bound together.
Eg. Starch (many glucose)

Question 54

What are the functions of carbohydrates/polysaccharides?

Answer 54

Polysaccharides (long chains of sugars) are used by organisms for either storage or structural purposes.

Storage of energy
Starch (in plants)
- Allows plants to stockpile surplus glucose for later use
- Most animals (including humans) can breakdown starch (from potato tubers, grains) into glucose for the cells’ energy.

Glycogen (in animals)
- Stockpile of surplus glucose in liver and muscle tissue

Cellulose (in plants)
- Major component of cell walls in plants
- Herbivores rely on cellulose-digesting microorganisms to digest it.
- In our diet cellulose is the main source of ‘dietary fibre’

Question 55

What are lipids?

Answer 55

The compounds called lipids are grouped together because they do not mix with water - they are hydrophobic. They have a hydrophilic head, but a hydrophobic tail.

There are 2 main types:
- Fats/oils (triglycerides)
- Phospholipids

Question 56

What are enzymes?

Answer 56

Enzymes are proteins that act as biological catalysts.

They dramatically speed up metabolic reactions without being consumed (they can be reused)

Most enzymes are intracellular, however some are extracellular (eg. digestive enzymes in the gut).

Question 57

How do enzymes work?

Answer 57

Each enzyme has an active site that has a complementary shape to a specific substrate

When the substrate binds to the active site the site changes shape and improves the fit (induced-fit model)

The reaction occurs because the active site provides a suitable environment for the reaction to begin

Question 58

How does pH impact enzyme function?

Answer 58

Low pH (acidic) or high pH (alkaline) environments can denature enzymes.

Each enzyme has an optimal pH
Eg, most work best at neutral pH (7),
pepsin in the stomach, works best in an acidic environment (pH 2).

Question 59

What does the graph of enzyme activity for pH look like?

Answer 59

An exponential increase toward the optimum pH, where the line is then mirrored back down after the point of optimum pH. Almost looks like a parabola.

Question 60

How does temperature impact enzyme function?

Answer 60

Low temperatures decrease enzyme activity because the enzyme and substrate are moving at slower speeds and therefore collide and bind less often

High temperatures decrease enzyme activity because H-bonds are disrupted leading to the denaturation of the enzyme

Question 61

What does the graph of enzyme activity for temperature look like?

Answer 61

Exponential increase towards optimum temperature, and then a sudden decrease (due to denaturation) past that point. It is NOT symmetrical like the pH graph.

Question 62

What are exchange surfaces?

Answer 62

To maintain homeostasis cells exchange materials with their environment.

Most cells in a multicellular organism are not in direct contact with the environment and require specific structures which are specialised exchange surfaces.

This involves absorption for ‘exchanges’

Question 63

What are the four properties of an effective exchange surface?

Answer 63

Thin - reduces the distance through which substances are absorbed

Moist - substances move faster in a dissolved state

Large surface area - increases the area on which substances can move

Extensive blood supply - moves nutrients and wastes to and from the exchange surface

Question 64

What is mechanical digestion?

Answer 64

Physical chewing to break down food.

Question 65

What is chemical digestion?

Answer 65

The breakdown of large molecules into smaller molecules by enzymes.

Question 66

How does chemical digestion in the stomach work?

Answer 66

The cells lining the walls of the stomach secrete gastric juice, which is mixed with food to create chyme.

Gastric juice contains:

Hydrochloric acid (HCl)
- low pH of approx 2. kills most bacteria
- starts protein breakdown.
- Activates pepsinogen into pepsin

Pepsin – an enzyme that breaks down protein (a protease).

Question 67

Why doesn’t gastric juice destroy stomach cells?

Answer 67

Epithelial cells in the stomach secrete mucus which protects stomach cells from auto-digestion.

Pepsin is released in an inactive form called pepsinogen, which is activated in the stomach by hydrochloric acid.

Question 68

Why is the small intestine effective at nutrient transportation?

Answer 68

The small intestine has the following features:
- Large surface area
- Contains large folds on the interior area called villi.
- Villi epithelial cells contain projections called microvilli.

Question 69

What are the two ways substances can be transported across the epithelium (layer of epithelial cells - cells which secrete stuff) of the villi and into blood capillaries?

Answer 69

Passive transport - not requiring energy

Active transport - requiring energy

Question 70

Passive transport:

Answer 70

Does NOT require energy.

Transports molecules from an area of high concentration to an area of low concentration (down their concentration gradient).

When the concentration of nutrients (such as amino acids) is higher in the small intestine and lower in the blood capillaries, the nutrients will move by passive transport (high concentration to low concentration).

Question 71

Active transport:

Answer 71

DOES require energy.

Transports molecules from an area of low concentration to an area of high concentration (against their concentration gradient).

Energy is required for this process to occur.

When the concentration of nutrients is lower in the small intestine and higher in the blood capillaries, the nutrients will move by active transport (low concentration to high concentration).

Question 72

What is facilitated transport?

Answer 72

A form of passive transport through proteins, where molecules must be encased in a protein before they can physically be absorbed.

Question 73

Is SHE bad?

Answer 73

Yes.

Question 74

What two SHE concepts should be avoided to get more marks?

Answer 74

Both application and communication together. Too easy.

Question 75

What’s in the stomach?

Answer 75

Water, glucose, amino acids/monopeptides

Question 76

Describe the villi.

Answer 76

Within a villi, a cylinder shaped small bud, there’s a lot of blood vessels. In the middle stemming down it, there’s this rod looking thing called a lacteal.

Lacteal absorbs and transports fat, soluble vitamins and fatty acids, while the blood takes and transports glucose and amino acids

Question 77

What is plant transpiration?

Answer 77

Plants release oxygen, and lose water - this is known as transpiration, occurs in stomata of the leaf

Question 78

What are stomata?

Answer 78

Stomata stop plant from losing too much water, on the bottom of the leaves

Stoma closes during day to avoid plant running out of water, opens at night

They are on the UNDERSIDE of leaves to make use of gravity

Question 79

What is the structure of a stoma?

Answer 79

Two sausage looking things which can bend to open and make a donut shape or close to make a seal.

Stomata consist of:
- Nucleus, a little dot at opposing tops (like yin and yang)
- Chloroplasts, littler dots which are all around
- Vacuole, yellow tube thing which is the same shape sausage shape but scaled down in the middle of each side
- The empty space is filled by guard cell
- And then there’s a cell wall

Question 80

Processes in the stomata:

Answer 80

CO2 goes in through the stomata

Oxygen + water is released out the stomata

Water is absorbed from roots, through the xylem (pipe thingy in the stem) and then out the stomata. Boom transpiration

Plants also have a phloem which is like the xylem but it allows two-way flow (adds back to the roots) and transports nutrients

Question 81

Water transport:

Answer 81

Root pressure -> active transport
1. The roots uptake minerals and nutrients by active transport
2. The high concentration of solute (minerals and nutrients) causes water to move into the root by osmosis, this increases root pressure
3. The water travels up the xylem due to cohesion of water and pressure
4. Water leaves the plant via transpiration

Question 82

What is osmosis?

Answer 82

Water moves from a low solute concentration to a high solute concentration through a semipermeable membrane.

Question 83

What are the three types of vessels?

Answer 83

Arteries
- carry oxygenated blood from the heart

Blood capillaries
- Allow exchange of materials in all tissues of the body by connecting arteries and veins
- Capillaries are in villi to allow absorption of nutrients

Veins
- Carry deoxygenated blood to the heart

Question 84

Why would further bodily extremities receive less oxygenated blood?

Answer 84

Parts of the body closer to heart have higher o2 concentration because muscles use oxygen - further extremities will use oxygen less readily as more oxygen will be used by that point

Question 85

Why are capillaries effective at what they do?

Answer 85

They are thin (1 cell thick)

Moist (allowing diffusion of nutrients and wastes)

Large surface area (created by extensive capillary networks)

Question 86

What is the structure of the respiratory system?

Answer 86

Air breathed in passes through the trachea which then branches into the bronchi, which branch even further into bronchioles.

These bronchioles terminate in tiny air sacs called alveoli (singular alveolus).

Question 87

What happens at the alveoli?

Answer 87

Oxygen moves from the alveoli to the blood through simple diffusion – this happens because the blood would have a low concentration of oxygen as the body is using oxygen

NOTE that blood is constantly flowing, so the oxygen will constantly diffuse from the alveoli to the bloodstream and it will not reach any sort of capacity

Carbon dioxide constantly diffuses from bloodstream to alveoli – carbon dioxide goes down the concentration gradient (high ox concentration to low ox concentration)

Question 88

Why is diffusion from the alveoli effective?

Answer 88

to increase rate of diffusion each alveolus has a thin wall of 1 cell thickness, less distance of o2 and co2 to travel and is moist to allow diffusion of gases (co2)

Question 89

How does diffusion in muscle work?

Answer 89

Capillary running through muscle

Lactic acid and carbon dioxide go from muscle to capillary

Oxygen and glucose goes from capillary to muscle

Question 90

What is the function of kidneys?

Answer 90

Kidneys filter and remove waste from the blood. What you don’t want to see in urine is glucose cause diabetes

Question 91

Why do we breathe in oxygen?

Answer 91

Cells require oxygen for cellular respiration.

Cellular respiration is the process by which glucose is broken down to release energy.

Question 92

Elements of the excretory system:

Answer 92

Kidneys: organs responsible for the filtering and removal of waste products from the blood, for excretion by the body.

Ureter: tubes that transport urine from the kidneys to the bladder.
Bladder: storage of urine prior to excretion.

Urethra: allows urine to exit the body (urination)

Question 93

What is the structural and functional unit of the kidney?

Answer 93

Nephron. There are 800,000 of them in one kidney.

Question 94

What is the structure of the nephron?

Answer 94

The nephron consists of 3 key parts:
- The glomerulus (ball of capillaries)
- The Bowman’s capsule (basically a filter that takes particles into the tubule based on their particle size)
- A long thin tubule.

Question 95

What are the two processes which create urine?

Answer 95

Filtration and reabsorption.

Question 96

How does filtration work in the bowman’s capsule?

Answer 96

components of the blood are forced at high pressure through the pores of the blood capillaries and into the Bowman’s capsule.

Filtered based on molecule size.

Everything inside the blood that passes into the Bowman’s capsule

EXCEPT

Very big things like the blood cells and big proteins.

They cannot fit through capillary pores.

Question 97

How does reabsorption work in the excretory system?

Answer 97

Glomerular filtration involves substances in the tubule filtrate that are essential to the body (e.g. water, glucose) which are reabsorbed (recycled)

98 - 99% of water is reabsorbed.

Question 98

What is found in filtrate and what isn’t?

Answer 98

In filtrate (small molecules):
Water
Salts
Glucose
Urea
Amino acids

Not in filtrate (larger molecules):
Blood cells
Proteins

Question 99

Organism hierarchy:

Answer 99

Cell, tissue, organ, system.

E.g:
Muscle cells form muscle tissue.

Muscle tissue combines with the nerve & connective tissues to form the heart (organ).

The heart combines with other structures (lungs, blood vessels, blood) to make up the circulatory system.

Question 100

What are stem cells?

Answer 100

Stem cells are undifferentiated cells produced in the bone marrow that can produce, by mitotic division, daughter cells that can differentiate (specialise for different functions)

All multicellular organisms begin as an undifferentiated cell.

The zygote divides by mitosis and soon the cells begin to differentiate (specialise)

Question 101

What does pluripotent mean?

Answer 101

Embryonic stem cells are pluripotent (can form any type of cell/tissue, except for the placenta)

Pluripotent means a cell can specialise to any form of tissue except for the placenta.

Question 102

What does multipotent mean?

Answer 102

Bone marrow stem cells are multipotent (can form several types of cell)

They are more limited than pluripotent cells.

Question 103

What are the four types of tissue?

Answer 103

Connective tissue, epithelial tissue, muscle tissue, nervous tissue.

These tissue types make up the entire human body.

Question 104

What is connective tissue?

Answer 104

a diverse and widely distributed type of tissue in the body that provides structural support, connects and binds different tissues and organs, and plays a key role in various physiological processes.

Question 105

What is epithelial tissue?

Answer 105

a type of tissue that forms the surfaces of body structures, lining organs, cavities, and passageways, and serves as a protective barrier while also facilitating absorption, secretion, and sensory functions.

Question 106

What is muscle tissue?

Answer 106

a specialized type of tissue in the body composed of cells (muscle fibers) that contract and generate force when stimulated, allowing for movement, stability, and various physiological functions.

Question 107

What is nervous tissue?

Answer 107

a complex tissue in the body consisting of specialized cells called neurons that transmit electrical and chemical signals, enabling communication and coordination within the nervous system and facilitating sensory perception, motor control, and cognitive functions.

Question 108

What are organs?

Answer 108

Organs are made up of different tissues to perform specific functions.

For example:
Gastrointestinal tract contains:
- Connective tissue between folds of intestine
- Muscle tissue around tubes
- Epithelial tissue lining tract

Question 109

What are systems?

Answer 109

Organs are arranged in systems so that they work together in a coordinated manner.

Organs can play a role in more than one system

For example:
The liver synthesises and secretes bile to help digest lipids (digestive system)

The liver synthesises and secretes hormones (endocrine system)

Question 110

How are cells different if they contain the same DNA?

Answer 110

Every cell contains identical DNA/genes

So, how can cells differentiate to have such different structures and functions?

Different cells have different genes that are either expressed (turned on) or not expressed (turned off)

Question 111

What is a function of stem cells?

Answer 111

In multicellular bodies, stem cells are constantly dividing to grow, or replace old and damaged cells